In my U.S. Pat. No. 4,626,592, issued Dec. 2, 1986, and in my reissue application Ser. No. 029,455, filed Mar. 23, 1987, I have shown, inter alia, that amines and amides are N,N-cyclodialkylated by reaction with an unstrained cyclic ether in the presence of a B subgroup metal oxide alkylation catalyst preferably a Group IV-B metal oxide such as titanium dioxide.
In French Pat. No. 851,178, published Jan. 4, 1940, it is indicated that N-alkyl-, N-cycloalkyl-, N-aralkyl-, and N-arylpyrrolidines are obtained by subjecting tetrahydrofuran and primary alkyl-, cycloalkyl-, aryalkyl-, or aryl amines at a high temperature to the action of dehydrating catalysts such as alumina, bauxite, the oxides of thorium, titanium and zirconium, the phosphates and borates of aluminum, zinc, cadmium, tin or silver, and silica gel. See also the abstract of this patent appearing in Chemical Abstracts, Vol. 36, Abstract 1957.sup.2 (1942). Over the years, alumina has generally been regarded as the most efficacious catalyst for gem cyclodialkylation reactions of this type.